This invention relates to a tray carton erecting machine and, more particularly, to an end panel folding and sealing apparatus which seals the end panels and end flaps of the tray cartons together to complete the erection of the tray carton from its blank.
Tray carton machines which erect tray blanks about articles to be packaged in the tray cartons are used extensively in the soft drink and beer industry to package either sets of individual beverage cans, or pair of twelve-pack cartons. These tray carton machines typcally package up to 100 cartons per minute and normally employ static folding bars for folding the end panels of the trays against the end flaps and holding them together while the glue previously applied between the end flaps and panels sets. Some of these machines, such as the one disclosed in U.S. Pat. No. 3,504,478 also employ an auxiliary end panel sealer which is actuated when the machine is shut down to complete the folding and sealing of the end panels and flaps of the tray carton then in the folding and sealing station.
Tray carton machines which employ the static folding bars encounter a problem. The static bars which both fold and press the end panels against the end flaps to complete the formation of the trays exert a drag on the end panels. This causes at least some of the tray cartons to be formed such that the end panels do not line up properly with the end flaps and side panels. The tray cartons are out of square. This problem is not only aesthetic but the projecting portions of the panels can catch on other trays or objects and the handling of these trays can be a problem.
Tray carton machines such as the one disclosed in U.S. Pat. No. 3,504,478 which utilize an auxiliary end panel sealer that is pneumatically operated can present additional problems. If the pneumatic system malfunctions the tray then in the folding and sealing station will not be sealed. If the problem is observed the tray can be removed from the machine. Otherwise the tray carton comes apart after being discharged from the machine.
The tray carton machine of the present invention is provided with a unique end panel folding and tray sealing assembly. The static end panel folding bar and the need for an auxliary end flap sealer is eliminated by the mechanism of the present invention.
The mechanism for folding the tray end panels and pressing the end panels against the tray end flaps includes a pair of folding plates mounted within the folding and sealing station adjacent to and on opposite sides of the tray conveyor. Each folding plate is rotatably attached at its lower ends of crank arms of a pair of cranks. The cranks are spaced from each other with one crank being located a distance downstream from the other crank, less than the length of the folding plate. The crank arms of the cranks extend parallel to each other and are equal in length. Thus as the cranks are rotated in unison, the folding plates, which are in contact with the tray end panels during the upper half of their cycles, move in the downstream direction as the plates are being raised and lowered to fold the end panels and press the end panels against the end flaps. The downstream movement of the folding plates during the folding of the end panels and the sealing of the tray substantially eliminates or reduces drag by the folding plates on the end panels. Thus the tray carton machine of the present invention can form trays which are insquare and at speeds of over 100 cartons per minute.
Another advantage of the present invention is the elimination of an auxiliary end panel folding mechanism. The crank mechanisms are driven by drive trains which not only synchronize the cycles of the folding plates with the movement of the tray conveyor but also stop the folding plates at the uppermost point of their cycles under a normal shutdown. The end panels of the tray in the station are pressed and held against the end flaps to seal the tray and no auxiliary mechanism or pneumatic controls are required to effect the sealing operation.